I remember I once have played PS1 version of this game. apparently there are many differences.

1-) in the PS1 version, I remember each player can have maximum of 2 buildings of the same type only.
2-) I also notice there are 5 tech levels in some PC versions; in the PS1, only 4 tech levels existed
3-) I also notice many new buildings in the online wikis that I have never see in the PS1 version (Tank repair building, thermal exchanger, etc)
4-) I remember the Evolved mission 1: I will be your best friend, it used to be mission 5 in the PS1 version with a maximum tech lvl 2 instead of 1. are there more mission differences? has there been some missions deleted?

are there more differences? also, how many PC versions exist? Becuz I recall I once played PC version which is very similar to the PS1 with only 4 upgrades and no new buildings. are these changes recent?

Here is a video on how the campaign map looks like in PS1 version
https://www.youtube.com/watch?v=V7mDhdacqhw&t=20s

https://www.youtube.com/watch?v=2px9UhRN9nY&t=14s

Here is you can see that max 4 upgrades are available always

https://www.youtube.com/watch?v=V7mDhdacqhw&t=5m26s