Just order the cake and ask the shop to write anything you like on it. Usually no additional cost.

If you want to buy oven (convection, not the microwave), then you can Google for any recipe. The simplest one is pound cake, like the one you can buy in Tesco. The reason it is called pound cake is because originally, all ingredients are 1 pound each. So, easy to remember, use same weight for everything, say:
1) Flour -- 300g
2) Sugar -- 300g
3) Egg -- 300g
4) Butter/Margarine -- 300g

Baking powder ... err not 300g ... maybe 2 teaspoon

Bake at 180C for 30~40 min (maybe?? I dunno). Cake is done when you insert a toothpick at the center and it come out clean.

There you go.

Yes. instead of baking in oven, you can steam. the cake is moist and nice

Fruit cake is best steam baked

Well, basically cakes are the same. The secret recipe cake are all the same cake layer, which is cheese cake. For blueberry they put blueberry jam/preserve between layer. For other flavor just put different jam

The birthday cake is just same cake inside. Outer layer is just icing and its decoration. I'm not cake expert but I've been making cookies and baking since primary school and so were my brothers. Our mother just let us handle the baking during festival I haven't bake for long time now