Yes, it is possible. Does that make it acceptable? Depends on the research. You are limited by availability, so you probably need to select a sample you can reach.

Define the population and identify the sample frame. Try to enlarge your sample, which means looking beyond what can be done minimalisticly. Size depends on your research paradigm (e.g., qualitative, quantitative, or mixed methods). Examine the concepts of convenience sampling, stratified, cluster, and snowballing, etc.

Justify your methods, your size, and acknowledge your limitations.

It depends on your purpose. For most of our research, we use convenience samples to show relationships among variables.

Yes you can but provided you give some reasoning and justification on why you adopted that method. Most probably you will do purposive sampling. This can be due to unique type of respondents or availability of those type of respondents etc. If the purposive sample is too small then also consider qualitative method to go deeper. All of which i have mentioned is however dependent on your research study objectives.

Yes, non-probability sampling is not exclusive to just one type, and several of the methods overlap. For example, you can use convenience and opportunistic sampling. You can also have a convenience sampling method and use a snowball sampling method thereafter. These are just examples, but of course it depends on your purpose, your needs, your study population, access to that population, and your research methodology to determine which sampling method is the right one for you. But, generally speaking, these sampling methods should be used for qualitative research (and only in certain circumstances for quantitative research).

يجب ان يكون عينات من نفس صنف ليبين نتائج صحيحه و واقعيه

Actually i also agree that non-probability sampling is not exclusive to just one type, and several of the methods overlap.

The primary aim of a line of research is to improve the conditions of the study population, ideally all of them, but this will not always be possible. For example, the population may be unreachable (too large); or unknown (no sampling frame); or it may be inaccessible (incompatible).

In principle, in the case of quantitative research, a probability sampling technique should be considered (simple random; systematic random; stratified or clustered), but in some cases and especially in qualitative research, a non-probability sampling method is justified (quota, snowball, criterion or convenience sampling).

However, the use of two non-probability sampling methods depends to a large extent on the statement of your study (purpose + line of inquiry + study population).

Abosede Oke try to use any one convenience sampling technique to collect optimal sample size from three of your target population groups (i.e., athletes, coaches, officials) to address the purpose of your study, as population size and purpose of the study are important determinants of sampling method and sample size.