1) Is "to call" an infinitive or an auxillary verb? If not what is an infinitive verb?
To call: This is an infinitive verb.
Yes, it is a complex sentence because one of its constituents is made up of a clause. In other words, it is a complex sentence because it has a main clause and a subordinate clause.2) Is "What if this PM asks people to trust him again?” a complex sentence
Your question is unclear. Let us have the following sentence and see the explanation below:
3) Is “so they can spend more time tackling drug dealers, muggers and yobs” an adverbial subordinate clause or is it more than one clause
They have hired more policemen so that they can spend more time tackling drug dealers, muggers and yobs.
have hired= Verb
More policemen= Object
so that......yobs= Adverbial
Therefore, if you are talking about: so....yobs, then it is one clause: an adverbial
But this adverbial already contains an embedded clause, which is: "tackling.....yobs"
For clarification, I would say: the clause that you have mentioned, if looked at as a constituent of the bigger sentence (the matrix sentence), is one unit" An Adverbial.
But if your question is simply: how many clauses are there in "So....yobs", then my answer is that we do have another clause embeded inside the adverbial clause.
Noun subordinate clause.4) In, “it will put us on the line in a way that no government has ever been before” is "that no government has ever been before” a relative or a noun subordinate clause