The probability is always 50/50 even if you flipped 100 or 1000000 coins.
The probability of flipping a fair coin four times and getting four heads is 1 in 16, or 0.0625. That is simply the probability of one head (0.5) raised to the power of 4.
Your question is a bit difficult to understand. I will rephrase it as follows: What is the probability of getting a head if a coin is flipped once? p = 0.5 What is the probability of getting 2 heads if a coin is flipped twice = The possible events are HT, TH, HH, TT amd all are equally likely. So the probability of HH is 0.25. What is the probability of getting at least on head if the coin is flipped twice. Of the possible events listed above, HT, TH and HH would satisfy the condition of one or more heads, so the probability is 3 x 0.25 = 0.75 or 3/4. Also, since the probability of TT is 0.25, and the probability of all events must sum to 1, then we calculate the probability of one or more heads to be 1-0.25 = 0.75
Fifty percent (50%)
The answer depends on how many coins are flipped, and how often.
The probability of getting at least one tail in a flip of six coins is the same as the probability of not getting all heads, which is 1 - (0.56), or 0.984375.
The probability that 2 flipped coins both come up heads is 0.52 or 0.25
The sample space is HH, HT, TH, HH. Since the HH combination can occur once out of four times, the probability that if a coin is flipped twice the probability that both will be heads is 1/4 or 0.25.
The probability of flipping Heads on a coin is 1 - a certainty - if the coin is flipped often enough. On a single toss of a fair coin the probability is 1/2.
It is 4*(1/2)4 = 4/16 = 1/4