1) 1 rax expansion is probably the most common thing here. But yea, marine/scv all in also viable. Whatever build you're going for, the marine/scv can be defeated by really good stalker control. Any sentries would purely to FF the ramp when he tries to get up it, cutting his army in half and making it easier to deal with. Considering the power of stalkers to kite and never ******* die it's pretty much up to the protoss to hold off that sort of thing. There's also cutesy builds like 2 or 3 rax marine pressure into expansion and you can tell they're doing that when they move out and they aren't bringing scvs along with them. Again, good stalker control is what you need.
2) This secondary scout can be denied by good marine control. A single marine can stutter step and kill a probe before it gets up the ramp. This requires really good reflexes from the Terran though.
Even then if you scout only 1 marine it suggests an add on is on the rax, but you cannot tell without scouting it.
This is sort of an anything build from the terran. He could be expanding, cheesing, teching, 2 raxing, pressuring, whatever. You're going to have to send in another unit a bit later and see what's up or go along with your own build and see what happens. Hopefully whatever build you're doing is optimal against whatever happens.
3) No.
No because a lot of 1 gate FE's can fight off 2 raxes (and just retreat up the ramp and sac the expansion if it's a 3 rax, add on immortals and make a game of it from there) and because if it's a reactor FE you've just crippled yourself.
4) Again impossible to really tell until you see it coming from his base.
5) Yea again a world of possibilities.
Defending 1/1/1 is less of "what units do I make?" and more of "just what the **** do I do?"
The basic steps (and this is really basic/vague cuz I don't play that fucked up race)
1) Build a robo bay and an obs. Have it out before 7:30 because that's when cloak tech finishes.
2) Keep stalkers in each mineral line waiting for the drop/banshee. You don't have to worry about where his army is because you have control of the towers and should see it coming, so keep your probes protected
3) Cut probes at about 30-40 if he hasn't expanded. You should have an obs that sees everything in his main until he gets a raven out (but by then you should have plenty of information). You want ~5 gates and a robo AND NOTHING ELSE. Pure gateway/immortal should destroy any kind of 1 base shenanigans that he tries, and trying to eke out tech or upgrades that cost a lot and do nothing whilst his army just rolls yours is unproductive.
4) There's probably heaps of little rules and this's and that's about holding 1/1/1's and reading the terran that step 3) loses to. This is what Yang and Light can tell you about and what you're going to have to learn by yourself through hundreds of 'OH THAT'S BULLSHIT!' games.
If he has expanded get storms asap and laugh as his shitty army just dies. Tanks do approximately 0 damage to chargelot/immortal/archon and marines get trashed by storms.
Even the smallest donations help keep sc2sea running! All donations go towards helping our site run including our monthly server hosting fees and sc2sea sponsored community tournaments we host. Find out more here.