As a note it is getting increasingly hard to check every prior Q&A post for repeat questions. However, some questions do occur frequently so please bear with the occasional repeat in the future.

Five Leagues questions

Does the Lair scenario always feature an aberration?

Yes.

When the rules say I encounter aberrations, how many do I encounter?

Thankfully only 1 unless the rules explicitly say otherwise. 

What do I do if the only activity I have in the campaign turn is travelling to a city?

You just end the turn but you may opt to Trade (using the normal pre-battle trade rules) during the turn in which you arrive. 

Five Parsecs questions

Can I ever have a turn where no battles happen?

Not as written: You would always fight an Opportunity mission if nothing else has come up. After further thinking though, I think it is fine if you want to lay low for a turn and recover from injuries. Just roll for events and pay upkeep.

Do I have to take an offered Patron job?

No, you can turn it down. This does not affect a known Patron either (they usually offer the job to multiple freelancers).

Do I have to progress a Quest?

No. You always make the "Determine Quest Progress" roll after playing a Quest mission but you can choose not to progress until you are ready if you need to recover or have other tasks to pursue first. If you prefer a bit of time pressure, roll 1D3: You must pursue the Quest within that number of campaign turns or it fails. 

Lore questions

5P: How much does Unity defend and garrison its colonies?

Colonies have to be able to defend themselves at least somewhat, so every colony will maintain some sort of militia. This can range from a bunch of weekend warriors to pretty regular looking military forces often led by veteran NCO's from the Unity armed forces. Corporate run colonies will have either corporate troops or well paid security forces. 

If a world is particularly value, at a critical location or near enemy controlled space, it is likely to also have regular troops stationed there. Depending on the colony this can range from a single platoon of bored troopers to a full mechanised assault battalion.

5P: Are the Enforcer unit supposed to be Unity law enforcement?

Unity employs Enforcer troops to deal with pirates, well armed criminal syndicates and Converted infiltration. They function as both a sort of galactic law enforcement, support to local governments and a first line of defence against raids.

The "Enforcer" enemy encounter will tend to represent local security forces which can range from upholders of law and order to militant thugs extorting the locals for protection money. 

5L: Can you talk about the "old gods" and the "new gods"?

Both are pantheons that are (or were) worshipped throughout the lands. The New Gods have generally supplanted the Old as their worshippers are more organised: Church building and organised religion is a New Gods phenomenon while the Old Gods tend to worshipped in more individualistic manners. Tension can exist and some communities discourage or forbid the worship of one or the other, though open hostility is rare. 

Doctrinally, the Old Gods are said to be capricious and erratic and are said to favour the bold and the fool hardy, while the New Gods are said to be exacting and demanding. They are said to favour the determined and the committed.