Stop bath will stop development immediately.
Take one film, split it in two parts, process them both the same way except the stop bath (use acid with one part, the other with water). Tell the difference.
Stop bath will lengthen the fixer [hypo] life. Water will shorting it
Now, do the same thing but several times storing the fixer in two different bottles. Tell the difference.
Stop bath with indicator is not only inexpensive, it tells you when the stop bath is going bad.
Water is more regular.
The comprehensive indicator tells you - with the appropriate experience - that there're more than one way of doing things. Equally valid and applicable.
1. Develop for 12.5 minutes.
2. Water "stop bath"
3. Fix for 8 minutes.
4. Wash thoroughly.
5. Hang to dry.
1. Agitation?
2. Time?
3. Why? Agitation?
4. Define "thoroughly"
5. How?
BUT the film was slightly fogged because I was loading it on the reel in the closet, pitch dark, when my roommate came in and turned on the light outside.
Do your own "changing bag"! When I was ten I made it with dark clothes (without ruining them) and was one of the first things I bought (not only useful for loading film)
So there was a little bit of light coming in through the cracks, and the film being 400 ISO it probably fogged it
A little bit of light is a little bit of light for any film
Congratulations for your first time!
Best
I washed for about a minute.

