Making a 100 LED Lamp
In comment, you have identified the LED forward voltage as 2.8 - 3.5 volts, which identifies them as white LEDs.

Now, at 100 mA, each LED will dissipate .28 to .35 watts (current times voltage) and let's be conservative and go for .35. Your two batteries will put out 4.2 volts at 11.2 amps (and yes, you got that right). So the power available is, again, current times volts or 47 watts. 47 watts divided by .35 watts/LED says that, in principle, you can drive 134 LEDs.

So what you can do is connect each LED to a resistor of about 10 ohms, which will give you something on the order of (4.2 - 3.5)/10, or 70 mA. Put all 100 LED/resistor pairs in parallel, and you should be in business.

Or maybe not, since if the LEDs are actually running at 2.8 volts, the current will be (4.2 - 2.8)/10, or 140 mA, for a total of 14 amps. So a better starting point would be 15 ohm resistors.

But first, you need to think real hard about cooling. Your LEDs plus resistors will be dissipating something like 40 watts. In the worst case, the LEDs alone will produce 35 watts, and you MUST find a way to cool them. For what you're doing, a professional would be hard-pressed to do the job, and just having at it as you seem to want to do is almost guaranteed to end in heartache. You'll need a metal mounting plate for the LEDs, and very aggressive cooling. A finned heatsink may or may not do the job, and water cooling may be necessary.

Your comment that "Maybe I will build a smaller model first just to test" is the most sensible thing you've said so far.