Reverse the files

tac command is reverse of cat. It writes each file to stdout, last line first.

If you want to reverse the whole file in vim you can do it by :%!tac 

Find number of lines selected in visual mode

Command: 𝐠 𝐂𝐓𝐑𝐋-𝐆.

					*g_CTRL-G* *word-count* *byte-count*
g CTRL-G		Prints the current position of the cursor in five
			ways: Column, Line, Word, Character and Byte.  If the
			number of Characters and Bytes is the same then the
			Character position is omitted.
			If there are characters in the line that take more
			than one position on the screen (<Tab> or special
			character), both the "real" column and the screen
			column are shown, separated with a dash.
			See also 'ruler' option.  {not in Vi}


							*v_g_CTRL-G*
{Visual}g CTRL-G	Similar to "g CTRL-G", but Word, Character, Line, and
			Byte counts for the visually selected region are
			displayed.
			In Blockwise mode, Column count is also shown.  (For
			{Visual} see |Visual-mode|.)
			{not in VI}