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I have a problem with writing in graphic 12h mode. There isn't cursor, but I set it.
Help.

The hardware cursor isn't visible in graphics mode. A font and cursor could have any size you want - you make the rules. You will have to draw it yourself, make it blink and also update the position by re-drawing it yourself.
I suggest you forget about the cursor and focus on drawing some pixel based font for now - using X, Y position for the raw pixels. Once you have some functions done so you can print text, you could add cursor emulation to get the same experience as if it where normal text mode.

The wiki has some material (in c) on drawing in protected mode and how to draw fonts. In 16Bit mode you could probably adapt the bitmap fonts a bit.

All these Cursor,0xB8000(Or where you write text to)etc,etc are available in Text Mode but are not available in Graphics Mode.
If you need to print text, you need to develop your own font structure and plot each pixel yourself.

It is somewhat like you need to program a VGA Driver or so.