No. For example, a 1 Developer Pack Sencha Complete bundle can be used by only one unique developer.
You should have received the activation code in the email you provided when you purchased Sencha Complete. If not (or if you lost it), please write an email to firstname.lastname@example.org to obtain the code.
No, if you buy Architect you will also need to purchase a license of Ext JS for every user of Architect. Another option would to buy Sencha Complete.