Can pesticides penetrate into fruits and vegetables as well as on their surface? Is it possible to completely remove pesticide residue?

These types of question about pesticides, a generic category, are asking for answers about 100's of different structures with a myriad of physicochemical properties, phase transfer coefficients, attenuation rates, etc. and cannot be answered definitively until a specific chemical structure is identified.  Consider  the answer for any one specific pesticide active ingredient to the question from the perspective of environmental chemodynamics.  Those compounds with comparatively low water solubility (e.g., for pesticides that would be anything in the low ppm)  can diffuse more readily through the surfaces waxes and cuticles of plant leaves and fruit.  Compounds with higher water solubility, would not penetrate as easily and stay on the surface (but nothing is 100% this or that).  However, compounds of intermediate solubility can penetrate through the cuticle into the leaf matrix and than cross from one side of the leaf by movement in the cell walls, which are not barriers to movement of anything (in plant physiology this route is called the apoplastic transport pathway as opposed to the symplastic pathway that involves crossing plasma membranes).  Whether they can cross membranes or not depends on the physicochemical properties, but if they diffuse into the phloem, they are likely to move into the maturing fruit.  Those types of compounds will not be removed by washing but will be attenuated to some percentage by other processing methods.  If you use GOOGLE Scholar and the appropriate search terms, many tens of papers have addressed the issue.  Unfortunately, only until recently have the putative modern pesticides been examined.   In the U.S. for example, organophosphate insecticides are very infrequently found on fruits and vegetables because their use has been highly circumscribed since the aftermath of the Food Quality Protection Act (1996).  In the U.S. most pesticide residues detected on food are neonicotinoid insecticides and some of the newer fungicides (e.g., those in the strobilurin chemical class), but few contemporary studies have looked at these specific chemical classes.  I did find one that is freely available and includes one neonicotinoid and one strobilurin fungicide (all registered within the last two decades) (Zarębska, M., Hordyjewicz-Baran, Z., Wasilewski, T., Zajszły-Turko, E., & Stanek, N. (2022). A new LC-MS method for evaluating the efficacy of pesticide residue removal from fruit surfaces by washing agents. Processes, 10(4), 793.)  Most residue washing studies show partial removal, thus still leaving pesticide residues.  I could go on, but if you would take time to read regulatory documents regarding the risk assessments for the pesticides prior to commercialization, I hope you would see that any health concerns are overblown and without any toxicological support when a proper risk assessment is conducted.  Nevertheless, the best reason to wash fruit and veggies is removal of bacterial pathogens.  I wouldn't worry about pesticide residues but when I go to a grocery store and watch everyone picking through the commodity bins to find the perfectly looking apple, etc., I'm very motivated to wash the fruit to protect myself from everyone else's microbiome (of course I'm also guilty of picking just the perfect looking fruit).  P.S.:  A lot of conventional as well as organic growers will use inorganic sulfur compounds as fungicides, often forming a whitish sheen on fruit after spraying.  Inorganic sulfur compounds will not penetrate and most likely to be easily washed off compared to other types of organic compounds.  Be aware that on certain fruits, kaolinite clay preparations will be used to prevent sunburn and potentially achieve some insect repellent properties.  Sprays of these preparations, such as one commercial one called Surround, will leave a heavy white particulate.  In the U.S., packing houses will wash this off.)