Of course, 10C, there may well be another answer to your 2nd question. Why did Tina try to murder Gill? Because she was no doubt under orders that if things went threepennies up, she had to silence her.
The problem some of you seem to have is that you want everything to be wrapped up in a nice little package marked 'i's dotted and 't's crossed'. Much of what we needed to know was revealed. The rest will no doubt be revisited in future series. And, most likely, not everything will be brought to a conclusion until Mr Mercurio runs out of steam. Maybe not even then.