Not by themselves.

However there are theories on how a super advanced civilisation could achieve your points 1 and 2:

1) Use black holes as a power source. This works by encasing a rotating black hole in a Dyson sphere where the inside is coated in perfect mirrors. Then you fire lasers across the inside to the other side (not into the black hole). (I think you fire your laser in the direction the black hole is rotating.) This light steals some of the black holes rotational energy and just keeps on building up as it bounces off the mirrors and around the black hole. As the energy builds you then bleed off the higher energy beams - this is your power source, likely the greatest power source ever to exist.

2) See (1) above. Now instead of bleeding off the energy in a reasonable way, you just keep the entire thing 100% sealed after you fire your first beams, and just let the runaway laser beams gain in energy for a much longer time. You might need stronger mirrors? This can now be weaponised as follows:

A) Do nothing. It'll eventually gain too much energy for your containment and explode. Literally a black hole bomb. So the way this strategy works is you find a suitable black hole near your enemy and build your Dyson sphere, start your laser ignition then leave. Eventually it'll explode and obliterate anything within range. I'm not quite sure what the range would be.

B) The above are ideas I learnt from a Kurzgesagt video. My humble addition to this ridiculous concept is instead of letting the thing become a bomb, just let the energies build way past power generation scales, but before your Dyson sphere breaks down, and open a directional channel, like imagine a cylinder with the same mirrors on the inside aimed like lenses and this cylinder sticks out from the sphere on the outside. Now open a hole in the shell for light to pour out into your cylinder lens "gun barrel" and ensure its aimed at a star system you want to obliterate. Now you have something potentially more powerful than any astrophysical/relativistic jet and on demand.

I like the direction but have a feeling that 1) the mirrors would give in at some point in time. There are no perfect mirrors. 2) the energy required to stabilize this contraption would be higher than what you could extract from the bh

They are just regions of spacetime with a lot of mass and very strong gravity.

1) They aren't power sources, but if they are spinning that rotational energy could theoretically be harnessed: https://en.wikipedia.org/wiki/Penrose_process

2) Uh, no?

kurzgesagt has a video about (spinning) black holes as an energy source: https://www.youtube.com/watch?v=ulCdoCfw-bY

If there was any evidence anything in the universe outside our planet had been artificially manipulated you would've heard about it.