Poppy seeds do have the potential for recreational use, however, the answers to your two questions depend very much on where you live.
I know here in Australia, the seeds are supposed to be washed and deactivated by some sort of exposure to radiation. I've also heard (no proof) that they add an emetic agent (makes you vomit) to discourage their large scale consumption.
One can, however, still get very high simply by adding more seeds. There are a number of concerns associated with this.
1. Because the washing process varies, the dose varies. That means that when one week you barely get wasted on 500grams and you step it up to 800 and it turns out that the first batch was washed well and the second wasn't and it knocks your head off. When you extend this idea to higher doses, it means that the dose you thought would get you there, instead sees you into a hospital bed. I recommend that you take half of whatever total dose you intend to have first, and wait at least 25-45 mins on an empty stomach, to get a rough idea of the strength before you hit the rest. Dosage wise, the amount of time you soak them matters quite a lot. 12 hours of soaking compared to 1 hour may mean the difference between an overdose and a mild high. Still, taking half of the total intended dose and waiting before you have the rest, is a pretty safe way to kick off.
Overdoses have been reported with 1-3 kilograms of poppy seeds, which gives you an idea of the dose you wanna stay away from initially. I'd stay away from any more than 300-400 grams for the first time, just to be careful. Washed or not, there is no way you're come to any harm with 300 grams soaked for 1 hour. Soaked in between 1 and 2.5 litres. (Just google the imperial equivalents, I can't be bothered switching it to ounces etc). To my knowledge this isn't actually illegal to do, but I'm no lawyer.
2. Certain antihistamines reduce nausea from either the actual morphine or from any nasty emetics they've added. They also tend to get rid of the pruritus (that terrible extremely itchy skin that you get sometimes with opiates). These however, have the tendency to reduce your level of consciousness which can be bad if you're close to the line anyway.
Pot is an excellent alternative. Its an excellent anti-emetic (stops vomiting) and is far less likely to cause any drop in conscious state worth worrying about. IMHO, the combo of pot and opiates is also rather enjoyable.
3. Planting them is supposed to be impossible due to the radiation, but their have been a number of criminal case prosecuted here for people growing them from common store bought seeds. So it is clearly possible but illegal. Here in Aus at least there have been some significant jail sentences handed out, even for personal use.
4. If you do try this, I would strongly recommend not mixing the poppy tea with alcohol or benzos. There are some unpredictable synergistic effects, that can significantly raise the likely hood of a fatal overdose, or choking on your own vomit. I spent a week in ICU and very nearly died with the combination. It is however, tempting to just pop those few xanax you have now that you've just finished peaking. IF you do mix benzos/alcohol and poppy seed tea, try to do it only when you have someone else with you.
Apart from those immediate risks, there are no long term problems with poppy seed tea that I'm aware of other than practical considerations. I first got wasted on 100grams soaked for an hour and it only took a week or two before I needed over 800grams soaked for 5 hours to have the same affect. It becomes hard to buy seeds in that quantity and there is only so many litres of foul tasting oily water you can drink in one setting. Of course addiction, urinary retention and constipation (can't pee, can't poop) are risks as with all opiates.
Sometime soon, I'm going to look into the other substance in poppies and get a better idea of any long term affects of taking them in large quantities.