Hi, 2 questions in 1 (nb: please assume that I have the highest level account, and solutions involving coding are fine):

1: I want to maintain a group (i.e. set/cohort/panel) of participants, each of which will have various information pre-associated with them. This information will then be used to personalise their survey. Am I right in saying that this can be achieved by: (i) establishing an external database of info; and then (ii) using POST to query said database. Is this correct? And if so, what would I use as the identifying key to query the database?

(Possibly) Relatedly:

2: I want each of my participants to have a unique username and password. I gather that one way to have unique log-ins is by giving each participant their own URL. However, that is not ideal for me, since I want to establish a single address (besides which I envisage that my participants will be highly likely to lose/forget such URLs). Is there a way of implementing a standard username/password log-in? Such a log-in system would not have to be 100% secure.

Many thanks.