Need Help in Integrating the multiple web to lead forms. Conditions: Form 1 will be intake form 2 & 3 is dependent on the first form so how do I integrate the whole process whereas first form also generates the Lead and other two will do the same.
From your description, it sounds as though you want to post your first form to the 2nd (and/or 3rd as appropriate), then submit them all together combined into one form at the same time. Your web master should be able to help you with the code to be able to do this.
Otherwise, you'd be attempting to perform an update to your leads via the web to lead form which isn't going to be successful without all the information. If anything, it would result in either incomplete lead generation or lead duplication.
Any fields that are related to Account, Opportunity and Contact that aren't standard Lead fields need to be custom fields that will get mapped to those respective objects during conversion. Note that they can also be on the same form and don't need to be on separate forms unless for some reason you need to break them up. If those fields are on Form 2 or Form 3 but not on Form 1, then they would be added to the final Form that is submitted to the Lead object.
Web to Lead isn't intended for use in updating existing Leads so you'll want to submit a combined form. You'll need a web developer to help you post from one form to the next. Each Form will need all the previous Form's fields as hidden fields to hold when received.
It would look a bit like this where what's in
[ ] is hidden from display:
Form1 -> ([Form1] + Form2) -> ([Form1 + Form2] + Form3)