Period as abbreviation and bullet point usages

Question

Usage questions surrounding period (.)

1. Plural after abbreviation do you add s?

   e.g. certificates->cert.s, environments->env.s, configurations->config.s?

2. as bullet points period or bracket goes first?

   e.g. i.) or ii).?

Answer 1

1. Wikipedia--Hart's Rules

When an abbreviation contains more than one full point, Hart's Rules recommends putting the s after the final one.

Ph.D.s

M.Phil.s

the d.t.s

2. This is subjective; there's no formal rule for how a bullet point should look