Is it possible to access old builds of the game? 

I'm trying to work out if I can get the 2025.4.2 build I think from just before the last update so I can see what updates have been made to the base game and excellent Mika mod since I last played both. Couldn't see an easy way so if anyone can help me out let me know, cheers

No it's not possible. We are hosting only the newest build. As for what changes were made since April's build, the current release contains only bug fixes. The next proper build with new content is planned for early July. We will list new content included in it on the dev journal

No worries - thanks for the prompt reply!

There wouldn't really be substantive changes for minor build changes. The major build changes come every three months: January, April, July, October. If it is an April 10th build vs April 2nd build, it's almost always just bug fixes.