1) 4MB in 7z/Zip format?
2) Is it bad if my game size less than 3mb? (<2mb? <1 mb? <500kb?)
PS Tic-80 games in exe format have over 2.76 mb.
4MB uncompressed, if you use any compression, it has to be taken care of by your program ITSELF.
No, it isn't bad, the final rating takes size AND ingenuity into account, so use your space wisely.
Also consider joining the discord server, you'll likely get more help and discussion there. https://discord.gg/ge3YuJheBY