The letter "R".
a
it has a right angle in there
It is an angle that on both sides it has a right angle
It could be capital letter A
An angle can be named with one capital letter.
There are no angles in the letter l it is a straight line That's not right. There is one angle in the Letter l. its a 180 degree angle.
an acute angle
If you mean which alphabet letter, an L has one right angle; a T has a right and left acute angle.
It's impossible to say; it varies from font to font. In a font like Eurostyle, the top angle may not even be acute.
acute angle
O