Hand one alkyl halide to a nucleophile and four reactions start at once, each a different transition state racing the others. SN2 and E2 are bimolecular — the reagent attacks in the rate-determining step, so a stronger, more concentrated base speeds them both. SN1 and E1 share a first step: the halide simply leaves, making a carbocation, and its rate depends only on how stable that cation is and how well the solvent can ionize the bond.
The conditions arbitrate. A tertiary centre is too crowded for SN2's backside attack but makes the most stable carbocation, so it favours SN1/E1. A bulky base can't reach the carbon at all — it grabs a β-proton instead, forcing E2. Polar protic solvent stabilizes ions and drives ionization. And heat tips the balance toward elimination, whose looser transition state has the higher activation energy and entropy.
Stereochemistry is the tell. SN2's backside attack gives clean inversion; SN1's flat carbocation is attacked from either face, giving a racemic mixture. So the product's handedness reports which mechanism actually ran.
The simulation stopped unexpectedly — the lesson continues without it. You can move on; nothing you did was wrong.