Can I split gas line for hob and oven?

I disagree with the previous answer. First a Gas Safe engineer needs to establish if the existing gas service pipework is big enough to cope with the additional gas appliances this is based on the assumption that you want to keep your existing cooker. Quote "if it would be possible split the feed" (an exercise in determining that the gas supply can cope with the additional demand) This can only be achieved by carrying out pipe sizing calcs that your Gas Safe installer should know how to do, as for your second point it is not a question of how long the flexible gas hose should be as they are a standard length but the wall plate that the gas pipe is connected to should be approx 750mm from finished floor level unless the gas appliance installation instructions state otherwise!

You can divide the pipe if you apply the pipe size equation and it’s within tolerance, don’t let some trigger happy plumber branch off the gas without doing the correct calculations as starving other appliance of gas ( undergassing ) can be dangerous

Yes no problem

As already stated by previous engineers as long as the pipe size equation is followed no problem should occur