You can use more forums for posting and all forums allowed to add signature

Simply it drives traffic to your site

Yes, you can use them. In fact you have to use them but mostly try to use Do Follow forum websites.

ya sure, you can use whatever you may be but it should be match with the guidelines of that forum posted sites.

Yeah you can select what is best for you. And forum posting is still effective to promote your website.

yes it is the method for increase backlink...

yes dear you do this this forum allow you to do this.

yes you can, by signature you can built backlink.

Signature
 

Yes you can add many websites links in your signature details. And this forum site also provides do follow links so that you can boost your site by just including them in signatures.

Using website links in a signature can increase your Backlinks for SEO and helps get visitors to your site. As long as it's relevant they should click away!

wow greate advice I always think that 1 link to the main page is the best way of linking in forum signatures

of course you can use more than one signature with different different web site