Is this top dead centre?

[Noreg]

I want to fix my camchain tensioner and check the clearances (cylinder head cover needs replacing). Is this correct for that?

[Grimly]

Yep, that's TDC.

[phydeauxmutt]

Yes, that is TDC, but be aware that the crank sees that position TWICE for every open/close sequence of the valves. If you are doing something like valve timing, it is also important to know whether you are at TDC on the compression/power cycle or the exhaust/intake cycle.

[bwringer]

Yep, you've got it right.

Where the ^%$#@! is TDC?

https://www.bwringer.com/gs/tdc.html

As stated, sometimes the position of the camshafts matters so you'd need to go around again.