i dont know if its legal to ask or not.

if not legal, just close the thread pls!

which amount i need to donate for donor forum access?

https://forums.d2jsp.org/info.php?p=30

It's 25$ to get your account screened.
Access is not guaranteed when donating

So anything under $25 can still get it, but not sure, right?

No, you need to donate at least 25$ in a single transaction to get the screening process.
Amounts below 25$ will not work for this.

gotcha, thanks!

No problem, as stated in the link I posted earlier, there is also the option to have someone else donate on your behalf and you offer fg in exchange.
More can be read here: https://forums.d2jsp.org/topic.php?t=71291037

https://forums.d2jsp.org/tools.php?a=3&c=1

How to access the donor forum:

1st Option:
https://forums.d2jsp.org/info.php?p=30
https://forums.d2jsp.org/donate.php

Here you must select the option "I want to donate on behalf of my own account." And make a single donation of at least $ 25. Remember that an account is checked against many factors. And the amount even above $ 25 does not guarantee that you will get access to the donor forum.

2nd Option:
https://forums.d2jsp.org/topic.php?t=71291037&f=34
https://forums.d2jsp.org/tools.php?a=3&c=1

Here you place your bid in fg for $. And someone else donates for you. Usually these amounts oscillate around 1000-1200fg for $ 25. There you can check how much others were offering for each donation amount