Can I rely on normal Rabanut Hechsher for freshly squeezed juice in Jerusalem market? And is there any difference between normal Rabanut and Mehadrin in regard to Maasrot.

ב"ה Shalom I must repeat what I have written in the past in regard to similar questions. First, it should be clear that there is no room to doubt the reliability of the Hecsher of the Rabbanut. A product which was under the supervision of a Talmid Chacham has a "Chazaka" of being kosher. (Pesachim 9a.) The Rabbanut hechsherim are to ensure that klal yisrael is eating kosher food, even those Jews who may not give eating kosher a second thought. We, therefore, owe great gratitude to the Rabbanut that most food establishments and products in Israel are kosher and that presenting non-kosher food items as kosher is punishable by law. Unlike abroad where in many places it is difficult to find kosher food, fortunately in Israel it is difficult to find non-kosher. This applies to meat, fruits and vegetables and any other food product. However, in order to ensure that klal Yisrael is eating kosher, the Rabbanut does not always follow the most stringent opinions in Halacha. Therefore, if you choose to take upon yourself more stringent observance or what is labeled as "mehadrin", it is your prerogative. However, any stringent observance does not diminish the basis of the Hechsherim of the Rabbanut. Having said that, I also must add that the "mehadrin" is not always clearly defined and uniform for each kashrut agency. This means, that each kosher organization decides where it wants to be more stringent, where it wants to take extra precaution and therefore declaring itself mehadrin or more mehadrin than another organization. There are some issues where mehadrin is somewhat clear and that is in regard to "glatt" meat for example, or in refraining from drinking milk from non-Jewish owned dairies. However, I am unable to tell you if the Rabbanut Mehadrin Jerusalem, does anymore in regard to ma'asrot than the regular Rabbanut Hechsher. But, as I made clear this does NOT make the basic product you have bought not kosher. All the best