I need informationb on halacha and birth control. thank you

I'm directing this question to Rabbi Becher, because I've had good luck getting completely intellectually satisfying answers from him in the past on closely related questions--but I'm open to anyone who feels they can hit a home run on this one: I am one of those people who have turned to religion in some measure at least because Rabbi Kelemen's incunabular argument from his "Permission to Receive" made it intellectually difficult, to say the least, not to believe that the Jews had a revelation from G-d at Sinai. However, from time to time I encounter or think of counterarguments. When I do, I like to address them with a rabbi. In this case, someone challenged the logic that all Jews must be descended from the group who witnessed G-d's presence in Sinai with this story, which seemed plausible to me: "How do you know you're really descended from such a group? How do you know your ancestor wasn't some devious Russian who observed 'Those Jews seem to be successful. I'll move to another town and tell everyone there I'm Jewish, and like that I and my progeny forever will become a part of this successful people.'?" For argument's sake, let's say the devious Russian was a woman. If such an event transpired in Russia or anywhere else, perhaps even more than once in human history, then doesn't it cast doubt on [A] the veracity of any individuals claim today to be Jewish and [B] the claim that anyone is descended from a group of people who experienced collective prophesy that day at Sinai (that is, couldn't everyone who claims to be a Jew today actually be descended from one of these devious gentiles)? The only problem I can find with the latter question is that there must have been at least some group publicly identified as Jews that the supposed copycats were interested in joining, but even that problem doesn't prove any one of us is actually descended from an authentic Jew. Thanks in advance for your help in fully trouncing these counter arguments. Good Shabbos.

please send me the scriptural requirements for the tithe. Give me the scriptural teaching on the third year tithe. thanks.

Please keep this confidential!!!!! I am an orthodox 25 year old with an 18 year old siter-in-law whom I really want to help. I dont want to do this the wrong way and am not sure if I can do anything at all but I thought maybe you would have an idea. My sister in law (obviously shalom bais is going to be an issue here) is 18 and wants to go to israel but is one of those people who has no direction and hasn't really done anything about it, she really expects everything to fall in her lap. I am afraid though that the one time people are going to try and teach her tough love, is the one time she needs help the most!!! She really wants to go to bar ilan for the year, which may have its positives for some but not as many as going to somewhere that will help her religious observation. She has no interest in being orthodox and has even less in learning. She is a regular teenager, who drinks and probably does drugs and is very into boys and her gashmias. My inlaws would love her to go to a seminary but she did not get into the only one she would apply to (mechalos ester - I think) which is probably for the better becasue she has friends going there. I dont think they know what to do with her and her school seems to just want her to graduate and be gone. I was very like her as a teenager, but as a boy there were yeshivas in israel that wanted to help me, I do not know what program would be good for her or how to get her to look into them, obviously trying to trick her into believing the idea was hers would be ideal becasue anything that comes from anyone else is just not going to be the right program. Everyone in her family wants her to go to israel and she is willing I just think if we can get her to agree to go to the right program it may just work. I know this is a wierd question for an email but I really dont know who else to ask, and I really cant give up on her now!!!!

1. I learned to daven from a conservative day school, now I'm frum and daven daily by myself but I'm still not sure what exactly is necessary in my morning davening please advice. 2. Arriving late to shul on shabbos or yontiv occurs naturally for people what should you do? Start as if davening just started or start where the shul is davening and finish with them? 3. I know everyone needs someone to depend on etc. in life but how do you go about finding the correct Rabbi for yourself? The one for halachic questions, kashrus questions, decision questions, shidduch questions, just questions?