It's difficult to prove a negative of this kind. Zelensky said the plan to attack Crimea didn't exist. If the Kremlin has compelling evidence, it's up to them to present it. Actually, it seems they did produce some such, but it was ridiculed in western venues, e.g. in The Atlantic Council, based on their apparent inconsistencies
On March 24, the pro-Kremlin Telegram channel Оперативные сводки (“Operative news”) published photos of medals and certificates that it alleged were going to be used to reward Ukrainian troops “for the capture of Crimea.” The post said the medals and documents were found in Ukrainian conscription offices. Another Telegram channel, Kremlin Z, claimed that these items were discovered in the city of Kherson, currently occupied by Russia. Russian media amplified this message, claiming that the medals were evidence that Ukraine, with the help of NATO, was planning to attack Crimea.
This appears to be the latest in a string of Russian false-flag allegations, due to the alleged evidence’s incorrect use of official Ukrainian terminology. Ukraine considers Crimea to be temporarily occupied or annexed by Russia, so if such materials were to exist, they would likely reference the “liberation” of Crimea rather than its “capture.” Further, official Ukrainian documents refer to Crimea as “the Autonomous Republic of Crimea” or “AR Crimea,” while materials allegedly found by Russia did not. The certificates also mention that the medal would be awarded under a Ukrainian presidential “order,” even though Ukrainian military personnel only receive awards via presidential “decree.” Notably, Russia itself uses the word “order” to describe ministerial awards and decrees for presidential awards, as documented in an investigation by Bellingcat.
And that "evidence" apparently also got Zelensky's initials wrong (in Ukrainian).
As for "another punitive operation in Donbas": it is too vague to be meaningfully confirmed or refuted. One drone strike on an a separatist artillery position (artillery which had been firing, according to Ukrainians) back in the fall of 2021 drew stern condemnation from Russia, and a gathering of troops at the border.
As the NYT recounted that incident:
Deployed for the first time in combat by Ukraine and provided by a country that is a member of the North Atlantic Treaty Organization, the drone hit a howitzer operated by the separatists. Things quickly escalated.
Across the border, Russia scrambled jets. The next day, Russian tanks mounted on rail cars rumbled toward the Ukrainian border. [...]
The troubles began about a month ago when separatists closed a checkpoint on their side — where local residents also traveled for shopping — for unclear reasons, possibly as a coronavirus precaution.
In response, on Oct. 25, Volodymyr Vesyolkin, the administrator of Hranitne, a position akin to mayor, led a contingent of about a dozen soldiers across the footbridge. The same day, the military laid concrete blocks for a new bridge about 700 yards away that would be accessible for vehicles.
His motive, Mr. Vesyolkin said, was humanitarian: to assure locals of access for shopping and deliveries of coal for winter heating.
“How can it violate anything?” Mr. Vesyolkin said in an interview. “This is our village. These are our people. They walk several kilometers to buy groceries.”
The separatists interpreted it otherwise — as a land grab — and soon their artillery shells filled the air.
Even Ukrainian military officers concede a misperception was possible. “They maybe thought we would send heavy weapons” across the new bridge, Major Sak said.
Through the night and into the next morning, a separatist unit with 122-millimeter artillery guns fired toward Ukrainian forces in what is known as a shoot-and-scoot maneuver intended to skirt counterattacks by the enemy.
In total, the separatists fired about 120 rounds at the unfinished new bridge, but every shot missed. They hit nearby houses instead, destroying one with such force that it appeared turned inside out, with a pile of cinder blocks covering the street.
Major Sak said he requested the drone strike because it was the only weapon that could hit the maneuvering enemy artillery and because civilians were in danger, though none were hit.
“Only modern weapons allow us to halt Russia’s aggression,” he said in an interview.
So it's hard to say what Putin meant exactly, but we know how the Russian forces reacted in the past to some events.
In the week leading to the Russian invasion proper, Ukraine reported some 70 (or 80) shelling incidents from the Russian [separatist] side in some 40 different locations. Some of these were confirmed by Western eyewitness/video accounts or otherwise documented on the ground. In the Kremlin's view, any Ukrainian [preparation for an] armed response to [any of] these probably would have satisfied Putin's claim that Ukraine was doing something "punitive".